Catalyst for synthesis of unsaturated aldehyde, production process for said catalyst, and production process for unsaturated aldehyde using said catalyst

ABSTRACT

The present invention provides: a production process for a catalyst for synthesis of an unsaturated aldehyde and/or an unsaturated carboxylic acid, which production process is suitable for producing the catalyst with good reproducibility, wherein the catalyst is excellent in activity, selectivity, and physical strength; this catalyst; and a production process for the unsaturated aldehyde and/or the unsaturated carboxylic acid by using this catalyst. The production process for the catalyst comprises the steps of: carrying out heat treatment of an aqueous solution or slurry of a starting material to thus prepare a catalyst precursor P 1 , wherein the starting material includes molybdenum, bismuth, and iron as essential components; thereafter adding and mixing a binder into the P 1  to thus prepare a catalyst precursor P 2 ; and molding and then calcining the P 2 , thereby producing the catalyst for synthesis of the unsaturated aldehyde and/or the unsaturated carboxylic acid; with the production process being characterized by involving an ignition loss ratio of the catalyst precursor P 1  in the range of 10 to 40 mass % (excluding 40 mass %).

BACKGROUND OF THE INVENTION

A. Technical Field

The present invention relates to: a production process for a catalystfor synthesis of an unsaturated aldehyde and/or an unsaturatedcarboxylic acid; this catalyst; and a production process for theunsaturated aldehyde and/or the unsaturated carboxylic acid by usingthis catalyst. More particularly, the present invention relates to: aproduction process for a catalyst for synthesis of an unsaturatedaldehyde and/or an unsaturated carboxylic acid, which production processis suitable for producing the catalyst with good reproducibility,wherein the catalyst is excellent in activity, selectivity, and physicalstrength; a catalyst as obtained by this production process; and aprocess comprising the step of carrying out catalytic gas phaseoxidation of at least one compound selected from the group consisting ofpropylene, isobutylene, t-butyl alcohol, and methyl t-butyl ether as araw material with molecular oxygen or a molecular-oxygen-containing gasin the presence of the above catalyst, thereby producing the unsaturatedaldehyde and/or the unsaturated carboxylic acid.

B. Background Art

Proposed are a lot of improved catalysts for carrying out catalytic gasphase oxidation of at least one compound selected from the groupconsisting of propylene, isobutylene, t-butyl alcohol, and methylt-butyl ether, thereby efficiently producing an unsaturated aldehydeand/or an unsaturated carboxylic acid that correspond to each.

For example, JP-A-013308/1975 and JP-A-047915/1975 disclose catalyststhat include Mo, Bi, Fe, Sb, and Ni, and further include at least oneelement selected from among K, Rb, and Cs as an essential component.JP-A-056634/1989 discloses catalysts that include Mo, Bi, and Fe, andfurther include at least one element selected from among Ni and Co as anessential component. JP-B-023969/1981 discloses catalysts that includeMo, Bi, and Fe, and further include at least one element selected fromIIA and IIB groups as an essential component.

As to the industrial use of the aforementioned catalysts,heat-exchange-type shell-and-tube reactors are generally used. However,the catalysts are packed while being dropped in a reaction tube having alength of several meters to ten and several meters wherein the reactiontube is settled in the above reactor, and therefore it is necessary thatthe above catalyst should also have sufficient physical strengthtogether in addition to the high activity and the selectivity of theobjective product.

In addition, on an industrial scale, catalysts are necessary in largequantities of several tons to dozens of tons, and therefore a personwith ordinary skill in the art would sufficiently recognize that: as toa catalyst as produced twice or more, the less the scatter of itsactivity, selectivity of the objective product, and physical strength is(the better their reproducibility is), the more favorable it is.

From such a point of view, there are also proposed a lot of processesfor producing a catalyst with good reproducibility, wherein the catalystis excellent in activity, selectivity of the objective product, andphysical strength.

For example, JP-A-253480/1993 discloses a process that involves carryingout salt decomposition in such a manner that the layer height of notless than 30 weight % of a dried product of catalyst is not lower than20 mm in a calcination stage. JP-A-238433/1996 discloses a process thatinvolves supporting a catalyst precursor on an inert support, wherein anitrate radical component and an ammonium radical component are removedfrom the catalyst precursor by carrying out heat treatment in thetemperature range of 200 to 400° C. JP-A-010587/1997 discloses a processthat involves carrying out salt decomposition of a dried product as acatalyst precursor by gradually adding it into a flowing gas that ismaintained in the temperature range of 200 to 450° C., and thereaftermolding and then calcining the resultant decomposed product.JP-A-096162/2001 discloses a process that involves molding and thencalcining a powder of a catalyst precursor having an ignition loss ratioof 1 to 5% after the ignition.

The above hitherto proposals (JP-A-253480/1993, JP-A-238433/1996,JP-A-010587/1997, and JP-A-096162/2001) as to the production process fora catalyst all relate to a process that involves removing a salt (e.g.nitrate salts and ammonium salts contained (remaining) in the catalystprecursor) from the catalyst. In these proposals, for example,JP-A-010587/1997 points out that the ammonium salts remaining in thecatalyst cause the scatter of chemical and physical properties of thecatalyst. In addition, JP-A-096162/2001 points out that the salts andvarious radical components in the catalyst precursor have an influenceon the catalyst performance.

However, there is a problem such that: the catalysts as produced bythese hitherto processes have been still insufficient in the activity,the selectivity of the objective product, and the physical strength fromthe industrial viewpoint, or the reproducibility is lacking for thecatalyst production. Therefore, it is desired to further improve thecatalysts.

SUMMARY OF THE INVENTION

A. Object of the Invention

Accordingly, an object of the present invention is to provide aproduction process for a catalyst for synthesis of an unsaturatedaldehyde and/or an unsaturated carboxylic acid, which production processis suitable for producing the catalyst with good reproducibility,wherein the catalyst is excellent in activity, selectivity, and physicalstrength. Another object of the present invention is to provide acatalyst as obtained by this production process. Yet another object ofthe present invention is to provide a process comprising the step ofcarrying out catalytic gas phase oxidation of at least one compoundselected from the group consisting of propylene, isobutylene, t-butylalcohol, and methyl t-butyl ether as a raw material with molecularoxygen or a molecular-oxygen-containing gas in the presence of the abovecatalyst, thereby producing the corresponding unsaturated aldehydeand/or unsaturated carboxylic acid.

B. Disclosure of the Invention

The present inventor has diligently studied in order to solve theabove-mentioned problems. As a result, he has found out that:surprisingly, contrary to the above hitherto known information, ratherin the case where a catalyst precursor as used when it is molded into ashape as actually used as a catalyst is allowed to contain a salt (e.g.nitrate salts and ammonium salts) in a definite amount range, theresultant catalyst is more excellent than conventional catalysts asproduced by conventional processes in respect of the catalystperformance and physical strength, and further the reproducibility inthe catalyst production is also enhanced.

Furthermore, the present inventor has also found out that there is noproblem in moldability if the amount of water as added to the abovecatalyst precursor is adjusted in a specific range.

The present invention has been completed in the above way.

That is to say, a production process for a catalyst for synthesis of anunsaturated aldehyde and/or an unsaturated carboxylic acid, according tothe present invention, comprises the steps of: carrying out heattreatment of an aqueous solution or slurry of a starting material tothus prepare a catalyst precursor P1, wherein the starting materialincludes molybdenum, bismuth, and iron as essential components;thereafter adding and mixing a binder into the P1 to thus prepare acatalyst precursor P2; and molding and then calcining the P2, therebyproducing the catalyst for synthesis of the unsaturated aldehyde and/orthe unsaturated carboxylic acid; with the production process beingcharacterized by involving an ignition loss ratio of the catalystprecursor P1 in the range of 10 to 40 mass % (excluding 40 mass %).

Hereupon, when the catalyst precursor P1 is uniformly mixed and about 10g thereof is accurately weighed out and then heated under air atmosphereat 300° C. for 1 hour, the ignition loss ratio of the catalyst precursoris calculated from the following equation:ignition loss ratio (mass %)=(mass of catalyst precursor−mass ofcatalyst precursor after heating)/mass of catalyst precursor×100.

Furthermore, water is favorably added and mixed as the binder in anamount of 5 to 30 parts by mass relative to 100 parts by mass of thecatalyst precursor P1.

In addition, a catalyst for synthesis of an unsaturated aldehyde and/oran unsaturated carboxylic acid, according to the present invention, isobtained by the above production process according to the presentinvention.

Furthermore, a production process for an unsaturated aldehyde and/or anunsaturated carboxylic acid, according to the present invention,comprises the step of carrying out catalytic gas phase oxidation of atleast one compound selected from the group consisting of propylene,isobutylene, t-butyl alcohol, and methyl t-butyl ether as a raw materialwith molecular oxygen or a molecular-oxygen-containing gas, therebyproducing the unsaturated aldehyde and/or the unsaturated carboxylicacid which correspond to the raw material; with the production processbeing characterized by using the above catalyst according to the presentinvention.

These and other objects and the advantages of the present invention willbe more fully apparent from the following detailed disclosure.

DETAILED DESCRIPTION OF THE INVENTION

As to the catalyst that is used in the present invention and includesmolybdenum, bismuth, and iron as essential components, any catalyst canbe used if the use thereof makes it possible to produce thecorresponding unsaturated aldehyde and/or unsaturated carboxylic acid bythe catalytic gas phase oxidation of at least one compound selected fromthe group consisting of propylene, isobutylene, t-butyl alcohol, andmethyl t-butyl ether as a raw material. However, favorably used is acomplex-oxide catalyst of a general formula (1) below:Mo_(a)W_(b)Bi_(c)Fe_(d)A_(c)B_(f)C_(g)D_(h)E_(i)O_(x)  (1)(where: Mo is molybdenum; W is tungsten; Bi is bismuth; Fe is iron; A isat least one element selected from among cobalt and nickel; B is atleast one element selected from among sodium, potassium, rubidium,cesium, and thallium; C is at least one element selected from amongboron, phosphorus, chrome, manganese, zinc, arsenic, niobium, tin,antimony, tellurium, cerium, and lead; D is at least one elementselected from among silicon, aluminum, titanium, and zirconium; E is atleast one element selected from among alkaline earth metals; and O isoxygen; and further, a, b, c, d, e, f g, h, i, and x denote atomicratios of Mo, W, Bi, Fe, A, B, C, D, E, and O respectively; and in thecase of a=12, the following inequalities are satisfied: 0≦b≦5; 0.1≦c≦10;0.1≦d≦20; 1≦e≦20; 0.001≦f≦5; 0≦g≦10; 0≦h≦30; and 0≦i≦5; and x is anumerical value as determined by the oxidation state of each element).

There is no especial limitation on starting raw materials of the abovecatalytic component elements. Ammonium salts, nitrate salts, carbonatesalts, chlorides, sulfate salts, hydroxides, organic acid salts, andoxides of metal elements as generally used for this kind of catalyst ora mixture thereof in combination may be used, but the ammonium salts andnitrate salts are favorably used.

An aqueous solution or slurry of a blend of the starting materials forthe catalyst may be prepared by a process as generally used for thiskind of catalyst. For example, aqueous solutions may be prepared fromthe above raw materials for the catalyst and then blended together inorder. There is no especial limitation on conditions for blending theraw materials for the catalyst (e g. blending order, temperature,pressure, and pH). There is also a case where the aqueous solution orslurry of the blend of the starting materials for the catalyst, asobtained in this way, is concentrated to dryness to obtain a cake solid,when the occasion demands. The aforementioned aqueous solution, aqueousslurry, or the cake solid of the blend of the starting materials for thecatalyst is heat-treated, thus obtaining the catalyst precursor P1.

There is no especial limitation on the heat treatment method forobtaining the catalyst precursor P1 and the form of the catalystprecursor. For example, a powdery catalyst precursor may be obtainedwith such as a spray dryer and a drum dryer, or a blockish or flakycatalyst precursor may be obtained by heating under a gas stream withsuch as a box-type dryer or a tunnel-type dryer.

The heat-treatment conditions are set in such a manner that the ignitionloss ratio of the catalyst precursor P1 will be in the range of 10 to 40mass % (excluding 40 mass %), favorably 13 to 37 mass %, more favorably15 to 35 mass %.

When the box-type dryer is, for example, used, the ignition loss ratioof the catalyst precursor P1 can be controlled by adjusting thetemperature and/or linear velocity of a heated gas and/or theheat-treatment time. The higher the temperature of the heated gas is, orthe faster the linear velocity of the heated gas is, or also the longerthe heat-treatment time is, the smaller the ignition loss ratio of thecatalyst precursor P1 can be made.

The ignition loss includes: such as a nitrate radical component and anammonium radical component that remain in the catalyst precursor P1 andbecome decomposed, volatilized, and sublimed by the heat treatment; andwater (The nitrate salts and the ammonium salts as contained in thecatalyst precursor P1 become decomposed by heating at high temperatureand thus removed from the catalyst precursor P1. That is to say, it ismeant that: the higher the ignition loss ratio of the catalyst precursoris, the higher the content of such as the nitrate salts and the ammoniumsalts in this catalyst precursor is.).

The above heat-treatment conditions such as the temperature of theheated gas and the linear velocity of the heated gas should fitly beselected according to the kind or properties of a heating apparatus(dryer), and they cannot be specified sweepingly. However, the catalystprecursor may be obtained by such as carrying out heat treatment under agas stream at a temperature of not higher than 230° C. for 3 to 24hours.

In the case where the ignition loss ratio of the catalyst precursor P1as obtained is not less than 40 mass %, it is favorable that: theconditions are changed, for example, in such a manner that thetemperature of the heated gas will be changed, and then the heattreatment is carried out again, thereby adjusting the ignition lossratio so as to be in the above range. In the case where a catalystprecursor P1 having an ignition loss ratio of not less than 40 mass % isused, the moldability is remarkably deteriorated in a subsequent moldingstep, and besides, the catalyst strength is also greatly lowered.

In the case where the ignition loss ratio of the catalyst precursor P1is less than 10 mass %, the catalytic activity and the yield of theobjective product tend to decrease.

The catalyst precursor P1 of which the ignition loss ratio has beenadjusted in the above way is subjected to a pulverization step or aclassification step for obtaining a powder having an appropriateparticle diameter when the occasion demands, and then it is transferredto a subsequent molding step.

Into the catalyst precursor P1 of which the ignition loss ratio has beenadjusted in the above range, a binder is subsequently added and mixed tothus prepare the catalyst precursor P2.

There is no especial limitation on the kind of the binder as added andmixed into the catalyst precursor P1. Examples thereof include publiclyknown binders usable for molding of catalysts, but water is favorable.

The amount of the binder as added and mixed into the catalyst precursorP1 (favorably the amount of the water as added and mixed into thecatalyst precursor P1) is in the range of 5 to 30 parts by mass,favorably 8 to 27 parts by mass, more favorably 11 to 24 parts by mass,relative to 100 parts by mass of the aforementioned catalyst precursorP1.

In the case where the amount as added is larger than 30 parts by mass,there is also a case where: the moldability of the catalyst precursor P2is deteriorated to such a degree that the molding cannot be carried out.In the case where the amount as added is smaller than 5 parts by mass,the binding between the catalyst precursors P2 is weak. Therefore, themolding itself cannot be carried out, or even if the molding can becarried out, the physical strength of the catalyst is lowered. In thecase of carrying out extrusion-molding, a molding machine is broken ifthings come to the worst.

The water as added to the catalyst precursor P1 can be added even in theform of an aqueous solution of various substances or a mixture ofvarious substances and water.

Examples of the substances as added together with the water include:molding assistants for enhancing the moldability; reinforcements andbinders for enhancing the catalyst strength; and substances that aregenerally used as pore-forming agents for forming pores in the catalyst.As to these substances, favorable are substances that do not have badinfluence on the catalyst performance (activity, and selectivity of theobjective product) by the addition. That is to say, favorable are: (1)an aqueous solution, or a mixture with water, of a substance that doesnot remain in the catalyst after the calcination; and (2) an aqueoussolution, or a mixture with water, of a substance that does not have badinfluence on the catalyst performance even if this substance remains inthe catalyst after the calcination.

Specific examples of the above (1) include: organic compounds, such asethylene glycol, glycerin, propionic acid, maleic acid, benzyl alcohol,propyl alcohol, butyl alcohol, and phenol; and nitric acid, ammoniumnitrate, and ammonium carbonate.

Specific examples of the above (2) include those which are generallyknown as reinforcements, such as silica, alumina, glass fibers, siliconcarbide, and silicon nitride. In the present invention, the catalyst asproduced has practically sufficient physical strength, but the abovereinforcements are added thereto when the still higher physical strengthis necessary.

In the case where the amount of the above substances as added is inexcess, the physical strength of the catalyst is remarkably lowered, andtherefore it is favorable to add them in such an amount not as does notlower the physical strength of the catalyst to such an extent that thecatalyst cannot be practically used as an industrial catalyst.

When the water is added in the form of the above aqueous solution ofvarious substances or mixture of various substances and water, forexample, when the molding is carried out by adding 20 parts by mass of 5mass % aqueous ethylene glycol solution to 100 parts by mass of thecatalyst precursor P1, the amount of the water as added to the P1 iscalculated as follows: 20×(1−0.05)=19 parts by mass.

The catalyst as used in the present invention may be either a moldedcatalyst as obtained by molding the catalyst precursor P2 into adefinite shape, or a supported catalyst as obtained by supporting thecatalyst precursor P2 on any inert support having a definite shape, butthe molded catalyst as obtained by molding the catalyst precursor P2into a definite shape is favorable.

In the case of the supported catalyst, such as alumina, silica,silica-alumina, titania, magnesia, steatite, and silicon carbide can beused as the inert support.

The method for molding the catalyst may be a hitherto publicly knownmethod. Applicable are molding methods such as an extrusion-moldingmethod, a granulation method (tumbling granulation apparatuses, andcentrifugal-fluid-coating apparatuses), and Marumerizer method. Of theabove, the extrusion-molding method is favorable.

As to the shape of the catalyst, any shape such as a column shape, aring shape, a spherical shape, and an irregular shape can be selected.

The average diameter of the catalyst is in the range of 1 to 15 mm,favorably 3 to 10 mm.

The molded structure as obtained is calcined under a gas stream in thetemperature range of 350 to 600° C. (favorably 400 to 550° C.) for about1 to about 10 hours, thus obtaining the objective catalyst for synthesisof an unsaturated aldehyde and/or an unsaturated carboxylic acid.

The catalyst as obtained in this way favorably has a ratio of theapparent density of the catalyst to the true density of the catalyst(apparent density of catalyst/true density of catalyst) in the range of0.25 to 0.55, more favorably 0.30 to 0.50.

Incidentally, in the present invention, the apparent density of thecatalyst is calculated as follows: apparent density ofcatalyst=1/(1/true density+pore volume).

In the case where the ratio of the apparent density of the catalyst tothe true density of the catalyst is less than 0.25, there is a casewhere the diffusion efficiency in the pores rises together with theincrease of the pore volume. In this case, the activity of the catalystand the selectivity of the objective product are enhanced, but there isa disadvantage in that the catalyst strength is remarkably lowered.

In the case where the ratio of the apparent density of the catalyst tothe true density of the catalyst is more than 0.55, contrary to theabove, the catalyst strength is enhanced, but there is a disadvantage inthat the activity of the catalyst and the selectivity of the objectiveproduct are remarkably lowered.

The pore volume of the catalyst is favorably in the range of 0.2 to 0.6cm³/g, more favorably 0.25 to 0.55 cm³/g.

There is no especial limitation on the production process whichcomprises the step of carrying out catalytic gas phase oxidation of atleast one compound selected from the group consisting of propylene,isobutylene, t-butyl alcohol, and methyl t-butyl ether as a raw materialwith molecular oxygen or a molecular-oxygen-containing gas, therebyproducing the unsaturated aldehyde and/or the unsaturated carboxylicacid which correspond to the raw material, except for using the presentinvention catalyst as a catalyst. This production process can be carriedout with generally used apparatuses, by generally used methods, andunder generally used conditions.

As is mentioned above, the raw gas as used in the above productionprocess for the unsaturated aldehyde and/or the unsaturated carboxylicacid is at least one compound selected from the group consisting ofpropylene, isobutylene, t-butyl alcohol, and methyl t-butyl ether, butthe propylene is favorable from the viewpoint such that the effects ofthe present invention can be displayed still more. That is to say, thepresent invention catalyst is favorably used for a process in which thepropylene is used as a raw gas, thereby producing acrolein (as theunsaturated aldehyde corresponding to the raw material) and acrylic acid(as the unsaturated carboxylic acid corresponding to the raw material).However, needless to say, the present invention catalyst is favorablyused also for a process in which at least one compound selected from thegroup consisting of isobutylene, t-butyl alcohol, and methyl t-butylether is used as a raw material, thereby producing the unsaturatedaldehyde and/or the unsaturated carboxylic acid that correspond to theraw material.

The catalytic gas phase reaction in the present invention may be carriedout by a conventional one-pass method or recycling method, and such asfixed-bed reactors, fluidized-bed reactors, and moving-bed reactors canbe used as reactors.

As to conditions of the above reaction, the reaction may be carried out,for example, by bringing a mixed gas into contact with the presentinvention catalyst in the temperature range of 250 to 450° C. under apressure of 0.1 to 1 MPa at a space velocity of 300 to 5,000 hr⁻¹ (STP),wherein the mixed gas includes: 1 to 15 volume % of at least onecompound selected from the group consisting of propylene, isobutylene,t-butyl alcohol, and methyl t-butyl ether as a raw gas; molecular oxygenhaving a volume ratio of 1 to 10 times relative to this raw gas; and aninert gas (e.g. water vapor, nitrogen gas, and carbon dioxide gas) as adiluent.

(Effects and Advantages of the Invention):

The present invention can provide: a production process for a catalystfor synthesis of an unsaturated aldehyde and/or an unsaturatedcarboxylic acid, which production process is suitable for producing thecatalyst with good reproducibility, wherein the catalyst is excellent inactivity, selectivity, and physical strength; a catalyst as obtained bythis production process; and a process comprising the step of carryingout catalytic gas phase oxidation of at least one compound selected fromthe group consisting of propylene, isobutylene, t-butyl alcohol, andmethyl t-butyl ether as a raw material with molecular oxygen or amolecular-oxygen-containing gas in the presence of the above catalyst,thereby producing the corresponding unsaturated aldehyde and/orunsaturated carboxylic acid. Therefore, the industrial value ofutilization of the present invention is extremely large.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention is more specifically illustrated bythe following examples of some preferred embodiments. However, thepresent invention is not limited to these examples in any way.

Incidentally, herein each of the conversion, selectivity, and yield isdefined as follows.Conversion (mol %)=(mols of reacted starting raw material)/(mols ofsupplied starting raw material)×100Selectivity (mol %)=(mols of produced unsaturated aldehyde andcarboxylic acid)/(mols of reacted starting raw material)×100Yield (mol %)=(mols of produced unsaturated aldehyde and carboxylicacid)/(mols of supplied starting raw material)×100

In addition, the true density and the pore volume of the catalyst weremeasured with the following apparatuses:

Measurement apparatus of true density: AutoPycnometer 1320 produced byMicromeritics Co., Ltd.

Measurement apparatus of pore volume: AutoPoreIII produced byMicromeritics Co., Ltd.

In addition, in the present invention, a value as measured by a methodbelow is used as an index for representing the physical strength of thecatalyst.

(Measurement Method for Catalyst Strength):

A stainless-steel-made reaction tube of 25 mm in inner diameter and5,000 mm in length is settled in a vertical direction, and the lower endof the above reaction tube is sealed with a stainless-steel-madereceiving plate of 1 mm in thickness. After about 50 g of catalyst isdropped from the upper end of the reaction tube into the reaction tube,the stainless-steel-made receiving plate as placed at the lower end ofthe reaction tube is removed, and then the catalyst is quietly extractedfrom the reaction tube. The catalyst as extracted is classified with asieve having a mesh opening size of 5 mm, and the mass of the catalystremaining on the sieve is weighed.Catalyst strength (mass %)=(mass of catalyst remaining on sieve)/(massof catalyst as dropped from upper end of reaction tube)×100

That is to say, the higher the value is, the higher the catalyststrength is.

CATALYST PRODUCTION EXAMPLE 1 Preparation of Catalyst (1)

While 10 L of pure water was heat-stirred, 1,500 g of ammonium molybdateand 96 g of ammonium paratungstate were dissolved therein, and 425 g of20 mass % silica sol was further added thereto. To this mixed liquid, aliquid as obtained by dissolving 1,030 g of cobalt nitrate, 618 g ofnickel nitrate, 229 g of iron nitrate, and 5.7 g of potassium nitrateinto 1,000 ml of pure water was dropwise added under vigorously stirredconditions. Subsequently, a liquid as obtained by dissolving 446 g ofbismuth nitrate into an aqueous solution was dropwise added theretounder vigorously stirred conditions, wherein the aqueous solution wasobtained by adding 250 ml of concentrated nitric acid to 500 ml of purewater. Then, the suspension as produced was heat-stirred, and therebythe major part of the water was evaporated, thus obtaining a cake solid.The cake solid as obtained was heat-treated with a box-type dryer(temperature of heated gas: 170° C., linear velocity of heated gas: 1.0m/sec, and heat-treatment time: 12 hours), thus obtaining a blockishcatalyst precursor. This catalyst precursor was pulverized, andthereafter its ignition loss ratio was measured. As a result, it was19.8 mass %. Next, pure water was added to the resultant catalystprecursor powder in a ratio of 150 g of the water to 1 kg of thecatalyst precursor powder, and the resultant mixture was kneaded for 1hour, and thereafter the mixture was extrusion-molded into a ring shapeof 6 mm in outer diameter, 2 mm in inner diameter, and 6 mm in height.Next, the resultant molded structure was calcined under a stream of airat 470° C. for 5 hours, thus obtaining a catalyst (1). The compositionof metal elements in this catalyst except for oxygen was as follows:catalyst (1): Mo₁₂W_(0.5)Co₅Ni₃Bi_(1.3)Fe_(0.8)Si₂K_(0.08).

In addition, the catalyst (1) had a ratio of its apparent density to itstrue density (apparent density of catalyst/true density of catalyst) of0.37, and further had a catalyst strength of 98.3 mass %.

As to the catalyst (1), the heat-treatment conditions, the ignition lossratio of the catalyst precursor P1, the kind of binder, the amount ofthe binder as added relative to 100 parts by mass of the catalystprecursor P1, the amount of the water as added relative to 100 parts bymass of the catalyst precursor P1, the ratio of the apparent density tothe true density (apparent density of catalyst/true density ofcatalyst), and the catalyst strength are summarized in Table 1.

CATALYST PRODUCTION EXAMPLE 2 Preparation of Catalyst (2)

In order to confirm the reproducibility, a catalyst (2) was obtained inthe same way as of Catalyst Production Example 1.

As to the catalyst (2), the heat-treatment conditions, the ignition lossratio of the catalyst precursor P1, the kind of binder, the amount ofthe binder as added relative to 100 parts by mass of the catalystprecursor P1, the amount of the water as added relative to 100 parts bymass of the catalyst precursor P1, the ratio of the apparent density tothe true density (apparent density of catalyst/true density ofcatalyst), and the catalyst strength are summarized in Table 1.

CATALYST PRODUCTION EXAMPLES 3 TO 11 Preparation of Catalysts (3) to(11)

Catalysts (3) to (11) were obtained respectively in the same way as ofCatalyst Production Example 1 except that: the heat-treatment conditions(temperature of heated gas, linear velocity of heated gas, andheat-treatment time) of the cake solid, and the amount of the binder asadded were changed in the preparation method of the catalyst (1) in theabove Catalyst Production Example 1.

As to the catalysts (3) to (11), the heat-treatment conditions, theignition loss ratio of the catalyst precursor P1, the kind of binder,the amount of the binder as added relative to 100 parts by mass of thecatalyst precursor P1, the amount of the water as added relative to 100parts by mass of the catalyst precursor P1, the ratio of the apparentdensity to the true density (apparent density of catalyst/true densityof catalyst), and the catalyst strength are summarized in Table 1.

CATALYST PRODUCTION EXAMPLE 12 Preparation of Catalyst (12)

While 10 L of pure water was heat-stirred, 1,500 g of ammonium molybdateand 96 g of ammonium paratungstate were dissolved therein, and 213 g of20 mass % silica sol was further added thereto. To this mixed liquid, aliquid as obtained by dissolving 1,360 g of cobalt nitrate, 206 g ofnickel nitrate, 372 g of iron nitrate, and 4.3 g of potassium nitrateinto 1,000 ml of pure water was dropwise added under vigorously stirredconditions. Subsequently, a liquid as obtained by dissolving 446 g ofbismuth nitrate into an aqueous solution was dropwise added theretounder vigorously stirred conditions, wherein the aqueous solution wasobtained by adding 250 ml of concentrated nitric acid to 500 ml of purewater. Then, the suspension as produced was heat-stirred, and therebythe major part of the water was evaporated, thus obtaining a cake solid.The cake solid as obtained was heat-treated with a box-type dryer(temperature of heated gas: 170° C., linear velocity of heated gas: 1.0m/sec, and heat-treatment time: 12 hours), thus obtaining a blockishcatalyst precursor. This catalyst precursor was pulverized, andthereafter its ignition loss ratio was measured. As a result, it was19.9 mass %. Next, 50 mass % aqueous ammonium nitrate solution was addedto the resultant catalyst precursor powder in a ratio of 280 g of theaqueous solution to 1 kg of the catalyst precursor powder, and theresultant mixture was kneaded for 1 hour, and thereafter the mixture wasextrusion-molded into a ring shape of 6 mm in outer diameter, 2 mm ininner diameter, and 6 mm in height. Next, the resultant molded structurewas calcined under a stream of air at 480° C. for 5 hours, thusobtaining a catalyst (12). The composition of metal elements in thiscatalyst except for oxygen was as follows:catalyst (12): Mo₁₂W_(0.5)Co_(6.6)Ni₁Bi_(1.3)Fe_(1.3)Si₁K_(0.06).

As to the catalyst (12), the heat-treatment conditions, the ignitionloss ratio of the catalyst precursor P1, the kind of binder, the amountof the binder as added relative to 100 parts by mass of the catalystprecursor P1, the amount of the water as added relative to 100 parts bymass of the catalyst precursor P1, the ratio of the apparent density tothe true density (apparent density of catalyst/true density ofcatalyst), and the catalyst strength are summarized in Table 1.

CATALYST PRODUCTION EXAMPLES 13 AND 14 Preparation of Catalysts (13) and(14)

Catalysts (13) and (14) were obtained respectively in the same way as ofCatalyst Production Example 12 except that the amount of the binder asadded was changed in the preparation method of the catalyst (12) in theabove Catalyst Production Example 12.

As to the catalysts (13) and (14), the heat-treatment conditions, theignition loss ratio of the catalyst precursor P1, the kind of binder,the amount of the binder as added relative to 100 parts by mass of thecatalyst precursor P1, the amount of the water as added relative to 100parts by mass of the catalyst precursor P1, the ratio of the apparentdensity to the true density (apparent density of catalyst/true densityof catalyst), and the catalyst strength are summarized in Table 1.

CATALYST PRODUCTION EXAMPLE 15 Preparation of Catalyst (15)

A catalyst precursor powder was obtained in the same way as of thepreparation method of the catalyst (12) in the above Catalyst ProductionExample 12. This catalyst precursor powder was pulverized, andthereafter 50 mass % aqueous ammonium nitrate solution was added to thecatalyst precursor powder in a ratio of 600 g of the aqueous solution to1 kg of the catalyst precursor powder, and the resultant mixture waskneaded for 1 hour, and thereafter an attempt was made to extrusion-moldthe mixture into a ring shape of 6 mm in outer diameter, 2 mm in innerdiameter, and 6 mm in height. However, the viscosity of the catalystprecursor rose to such an extent that the molding could not be carriedout, and therefore the molding was stopped.

CATALYST PRODUCTION EXAMPLE 16 Preparation of Catalyst (16)

A catalyst precursor powder was obtained in the same way as of thepreparation method of the catalyst (12) in the above Catalyst ProductionExample 12. This catalyst precursor powder was pulverized, andthereafter 50 mass % aqueous ammonium nitrate solution was added to thecatalyst precursor powder in a ratio of 90 g of the aqueous solution to1 kg of the catalyst precursor powder, and the resultant mixture waskneaded for 1 hour, and thereafter an attempt was made to extrusion-moldthe mixture into a ring shape of 6 mm in outer diameter, 2 mm in innerdiameter, and 6 mm in height. However, extraordinary noises were madefrom a molding machine, and extraordinary vibrations also occurred, andtherefore the molding was stopped.

CATALYST PRODUCTION EXAMPLE 17 Preparation of Catalyst (17)

While 10 L of pure water was heat-stirred, 1,500 g of ammonium molybdateand 382 g of ammonium paratungstate were dissolved therein, and 213 g of20 mass % silica sol was further added thereto. To this mixed liquid, aliquid as obtained by dissolving 1,442 g of cobalt nitrate, 429 g offerric nitrate, and 83 g of cesium nitrate into 1,000 ml of pure waterwas dropwise added under vigorously stirred conditions. Subsequently, aliquid as obtained by dissolving 515 g of bismuth nitrate into anaqueous acidic solution was dropwise added thereto under vigorouslystirred conditions, wherein the aqueous acidic solution was obtained byadding 250 ml of concentrated nitric acid to 500 ml of pure water. Then,the suspension as produced was heat-stirred, and thereby the major partof the water was evaporated, thus obtaining a cake solid. The cake solidas obtained was heat-treated with a box-type dryer (temperature ofheated gas: 170° C., linear velocity of heated gas: 1.0 m/sec, andheat-treatment time: 12 hours), thus obtaining a blockish catalystprecursor. This catalyst precursor was pulverized, and thereafter itsignition loss ratio was measured. As a result, it was 21.0 mass %. Next,50 mass % aqueous ammonium nitrate solution was added to the resultantcatalyst precursor powder in a ratio of 230 g of the aqueous solution to1 kg of the catalyst precursor powder, and the resultant mixture waskneaded for 1 hour, and thereafter the mixture was extrusion-molded intoa ring shape of 5.5 mm in outer diameter, 2 mm in inner diameter, and5.5 mm in height. Next, the resultant molded structure was calcinedunder a stream of air at 500° C. for 5 hours, thus obtaining a catalyst(17). The composition of metal elements in this catalyst except foroxygen was as follows:catalyst (17): Mo₁₂W₂Co₇Bi_(1.5)Fe_(1.5)Si₁Cs_(0.6).

As to the catalyst (17), the heat-treatment conditions, the ignitionloss ratio of the catalyst precursor P1, the kind of binder, the amountof the binder as added relative to 100 parts by mass of the catalystprecursor P1, the amount of the water as added relative to 100 parts bymass of the catalyst precursor P1, the ratio of the apparent density tothe true density (apparent density of catalyst/true density ofcatalyst), and the catalyst strength are summarized in Table 1.

TABLE 1 Heat-treatment conditions Catalyst Binder Amount Apparent Linearprecursor Amount of water density of Catalyst Temperature velocity ofHeat-treatment P1 Ignition as added as added catalyst/true CatalystProduction Catalyst of heated gas heated gas time loss ratio (parts by(parts by density of strength Example number (° C.) (m/sec) (hours)(mass %) Kind mass) mass) catalyst (mass %) 1 (1) 170 1.0 12 19.8 Pure15 15 0.37 98.3 water 2 (2) 170 1.0 12 19.6 Pure 15 15 0.37 98.5 water 3(3) 170 1.0 5 40.5 Pure 7 7 0.24 95.2 water 4 (4) 170 1.0 20 14.7 Pure17 17 0.42 98.6 water 5 (5) 170 0.7 12 29.8 Pure 11 11 0.31 98.0 water 6(6) 170 1.3 12 15.3 Pure 17 17 0.43 98.3 water 7 (7) 130 1.3 24 35.6Pure 9 9 0.29 97.7 water 8 (8) 130 1.0 10 40.8 Pure 7 7 0.24 95.6 water9 (9) 130 1.0 10 41.9 Pure 7 7 0.23 95.3 water 10 (10) 210 0.6 8 11.8Pure 19 19 0.48 98.9 water 11 (11) 210 1.0 15 4.4 Pure 21 21 0.57 99.1water 12 (12) 170 1.0 12 19.9 AN* 28 14 0.33 97.4 13 (13) 170 1.0 1219.6 AN* 50 25 0.27 96.4 14 (14) 170 1.0 12 19.5 AN* 14 7 0.47 98.5 15(15) 170 1.0 12 20.0 AN* 60 30 Impossible to mold 16 (16) 170 1.0 1219.7 AN* 9 4.5 Impossible to mold 17 (17) 170 1.0 12 20.0 AN* 23 11.50.34 97.0 *50 mass % aqueous ammonium nitrate solution

EXAMPLES 1 TO 10 AND COMPARATIVE EXAMPLES 1 to 4

Each of the catalysts (1) to (14) as obtained in Catalyst ProductionExamples 1 to 14 was packed into a stainless-steel-made reaction tube of25 mm in inner diameter as heated with a molten nitrate salt in such amanner that the layer length would be 1,000 mm, and then a catalytic gasphase oxidation reaction of propylene was carried out by introducing areaction gas having the following composition at a space velocity of1,500 hr⁻¹ (STP). The results are listed in Table 2.

-   -   Propylene: 6 volume %    -   Air: 55 volume %    -   Water vapor: 30 volume %    -   Nitrogen: 9 volume %

TABLE 2 Apparent Total density of Total yield of selectivity ofcatalyst/true Catalyst Reaction Conversion of acrolein and acrolein andCatalyst density of strength temperature propylene acrylic acid acrylicacid number catalyst (mass %) (° C.) (mol %) (mol %) (mol %) Example 1(1) 0.37 98.3 310 98.2 92.2 93.9 Example 2 (2) 0.37 98.5 310 98.2 92.494.1 Comparative (3) 0.24 95.2 310 98.4 91.9 93.4 Example 1 Example 3(4) 0.42 98.6 310 97.6 91.8 94.1 Example 4 (5) 0.31 98.0 310 98.4 92.093.5 Example 5 (6) 0.43 98.3 310 97.6 91.9 94.2 Example 6 (7) 0.29 97.7310 98.4 91.9 93.4 Comparative (8) 0.24 95.6 310 98.0 91.8 93.7 Example2 Comparative (9) 0.23 95.3 310 98.1 91.2 93.0 Example 3 Example 7 (10)0.48 98.9 310 97.2 91.2 93.8 Comparative (11) 0.57 99.1 310 94.6 88.994.0 Example 4 Example 8 (12) 0.33 97.4 310 98.4 92.4 93.9 Example 9(13) 0.27 96.4 310 98.7 92.3 93.5 Example 10 (14) 0.47 98.5 310 97.791.8 94.0

EXAMPLE 11

The catalyst (17) as obtained in Catalyst Production Example 17 waspacked into a stainless-steel-made reaction tube of 25 mm in innerdiameter as heated with a molten nitrate salt in such a manner that thelayer length would be 1,000 mm, and then a catalytic gas phase oxidationreaction of isobutylene was carried out by introducing a reaction gashaving the following composition at a space velocity of 1,500 hr⁻¹(STP).

-   -   Isobutylene: 6 volume %    -   Air: 65 volume %    -   Water vapor: 10 volume %    -   Nitrogen: 19 volume %

At a reaction temperature of 340° C., the conversion of the isobutylene,the total yield of methacrolein and methacrylic acid, and the totalselectivity of methacrolein and methacrylic acid were 98.1 mol %, 86.5mol %, and 88.2 mol % respectively.

Various details of the invention may be changed without departing fromits spirit not its scope. Furthermore, the foregoing description of thepreferred embodiments according to the present invention is provided forthe purpose of illustration only, and not for the purpose of limitingthe invention as defined by the appended claims and their equivalents.

1. A process for preparing an unsaturated aldehyde and/or an unsaturatedcarboxylic acid, which comprises the step of carrying out catalytic gasphase oxidation, with a catalyst, of at least one compound selected fromthe group consisting of propylene, isobutylene, t-butyl alcohol, andmethyl t-butyl ether as a raw material, with molecular oxygen or amolecular-oxygen-containing gas, thereby producing the unsaturatedaldehyde and/or the unsaturated carboxylic acid which corresponds to theraw material; with said catalyst being produced by a preliminaryproduction process which comprises the steps of: carrying out heattreatment of an aqueous solution or slurry of a starting material tothus prepare a catalyst precursor P1, wherein the starting materialincludes molybdenum, bismuth, and iron as essential components;thereafter adding and mixing a binder into the catalyst precursor P1 tothus prepare a catalyst precursor P2; and molding and then calcining thecatalyst precursor P2, thereby producing the catalyst for synthesis ofthe unsaturated aldehyde and/or the unsaturated carboxylic acid; withthe preliminary production process involving the step of controlling anignition loss ratio of the catalyst precursor P1 in the range of 10 to40 mass % (excluding 40 mass %) by adjusting at least one of atemperature of a heated gas, a linear velocity of a heated gas, and aheat-treatment time in carrying out said heat treatment of an aqueoussolution or slurry of a starting material, and, when the catalystprecursor P1 is heated under air atmosphere at 300° C. for 1 hour, theignition loss ratio of the catalyst precursor P1 is calculated from thefollowing equation: ignition loss ratio (mass %)=((mass of catalystprecursor P1 which has been prepared by said step of carrying out heattreatment of said aqueous solution or slurry of said startingmaterial)−(mass of catalyst precursor P1 after catalyst precursor P1 hasbeen heated under air atmosphere at 300° C. for 1 hour))/(mass ofcatalyst precursor P1 which has been prepared by said step of carryingout heat treatment of said aqueous solution or slurry of said startingmaterial)×100.
 2. An aldehyde/acid production process according to claim1, wherein water is added and mixed as the binder in an amount of 5 to30 parts by mass relative to 100 parts by mass of the catalyst precursorP1.
 3. An aldehyde/acid production process according to claim 1, whereinsaid catalyst has a ratio of the apparent density of the catalyst to thetrue density of the catalyst (apparent density of catalyst/true densityof catalyst) in a range of 0.25 to 0.55.